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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

FIG. 15.

Igo                                 VANADIUM STEELS

fused with sodium carbonate in a platinum crucible, this mass being also

lixiviated with water.

The two aqueous solutions, which contain all the vanadium as sodium
vanadate, are together boiled to decompose the excess of peroxide, evaporated
to 30-40 'c.c., and poured into the flask of the Bunsen apparatus (see Fig.
15), the vessel being rinsed out with very little water.

The alkaline liquid is neutralised with cone, hydrochloric acid free from

chlorine, the yellowish solution
being then mixed with 30 c.c.
of cone, hydrochloric acid and
1-3 grams of potassium bro-
mide.     The apparatus is ar-
ranged as shown in the figure,
the conducting tube from the
flask being  dipped  into   the
potassium     iodide      solution
(5-10    grams    of    potassium
iodide free  from iodate) con-
tained in the retort  fixed  so
as to be rotatable.

The liquid is then slowly
heated to boiling, the retort being turned at intervals to expel the
accumulated air ; the boiling is continued for about 10 minutes. With-
out uiterrupting the heating, the retort is removed, the conducting tube
being rinsed with water. The retort is then cooled, emptied into a beaker
and rinsed out several times, first with water and then with potassium
iodide solution. The liberated iodine is titrated with thiosulphate in the
usual way : I c.c. N/io-thiosulphate = 0-005106 gram of vanadium.1

If the liquid from the lixiviation of the fused mass appears yellow owing
to the presence of chromates, it is necessary to eliminate the chromium
before titrating the vanadium. After the liquid has been boiled to decom-
pose the excess of sodium peroxide, it is neutralised exactly with nitric
acid and treated with mercurous nitrate to precipitate the chromium,
vanadium, etc. (see Analysis of Chrome Steels). The precipitate is collected
on a filter and washed and ignited in a platinum crucible to expel the mercury,
the residue being fused with sodium carbonate and bitartrate and the
resultant mass lixiviated with hot water. In the residue insoluble in water
the chromium is determined, and in the alkaline solution the vanadium,
by the method already given.

2.  Determination of the Carbon, Silicon, Manganese, Phosphorus
and Sulphur.—See Analysis of Ordinary Steels (Iron, i, 2, 3, 4, 5).

3.  Determination of the Nickel.—As in nickel steels.

4.  Determination of the Molybdenum.—When  the  reduction  of

1 If the vanadium is present in very small quantity, it is necessary to dissolve 10-15
grams of the sample in hydrochloric acid, to eliminate the iron by means of ether in
Rothe's apparatus, to evaporate the hydrochloric acid solution containing the vanadium
with sulphuric acid and to fuse the sulphates obtained with sodium hydroxide and
sodium peroxide to transform the vanadium into sodium yanadate.HBr =